In 1643, Evangelista Torricelli ( 1608-47 ) He devised a method for measuring atmospheric pressure and constructed the first mercury barometer. This barometer is, in essence, in a long glass tube, of about 100 cm in length, closed on one end, which is filled completely with mercury. Avoiding mercury 40 is poured; plugging the open end of the tube ) reverses the tube and introduced its open end into a bucket containing mercury, placing the tube in a vertical position, as shown in the figure. Torricelli did this experience and noted that the mercury levels went down inside the tube until remained a 40 column; column barometric ) about 760 mm above the level of the mercury in the reservoir.
